Recovery of quinoline



United States Patent 9 2,999,794 RECOVERY OF QUINOLINE Donald J. Foster,South Charleston, and Denvil E. Reed,

Charleston, W. Va., assignors to Union Carbide Corporation, acorporation of New York No Drawing. Filed Sept. 24, 1958, Ser. No.762,915 18 Claims. (Cl. 202-42) The present invention relates to theseparation of organic compounds, and more particularly, to an improvedprocess for recovering quinoline from a mixture with aromaticnitrogen-containing compounds.

The quinoline-containing mixtures with which this invention is concernedare those of the type produced, for example, by the liquid-phasehydrogenation of coal. In such a process, quinoline can be obtained inadmixture with other aromatic nitrogen-containing compounds, andparticularly with aromatic primary and tertiary amines, by distillationof the crude hydrogenation product. It is in association with thisprocess, viz. the production of quinoline by the liquid-phasehydrogenation of coal, that especial advantage has been found to accruein accordance with the practice of the invention. However, the inventionis not limited in this respect, and can be employed to recover quinolinefrom any similar mixture of arcmatic nitrogen-containing compounds,notwithstanding the manner in which the mixture was initially obtained.For example, the process of the invention can be employed to recoverquinoline from a mixture with other aromatic nitrogen-containing coaltars, such as that obtained as a by-prodnct during the coking of coal.The invention also finds suitable use in the recovery of quinoline fromthe crude reaction product formed by conventional processes for theproduction of quinoline from alkyl-substituted anilines.

Illustrative of the broad range of compounds found in thequinoline-containing mixtures contemplated by the invention there can bementioned isoquinolines, alkylsubstituted quinolines, aniline,alkyl-substituted anilines, pyridine, alkyl-substituted pyridines andthe like. Generally, aromatic nitrogen compounds of this nature evidencebasic characteristics in that they are reactive with acids, particularlydilute mineral acids. Consequently, such compounds are commonly known asaromatic nitrogen bases, and will hereinafter so be defined.

In the past, various processes for recovering quinoline from a mixturewith other aromatic nitrogen bases have been proposed by the art.Illustrative of these are processes involving either (a) fractionaldistillation of the mixture, or (b) the formation of aromatic nitrogenbase salts by the addition of mineral acids, such as phosphoric orsulfuric acids, to the mixture, followed by the selective extraction ofthe quinoline salt from the resulting mixture by means of a suitablesolvent, such as water or alcohol. Unfortunately, however, the use ofthese recovery techniques has not met with complete satisfaction,particularly when they are utilized to separate quinoline from aromaticnitrogen base mixtures in which compounds possessing physical propertiesclose to or in common with the desired product are also present, and inwhich the initial concentration of quinoline is low.

For instance, it is at least difficult to distill a quinoline product ofhigh concentration from an aromatic nitrogen base mixture such as thatobtained by coal hydrogenation, containing in addition to quinolinesubstantial quantitles of alkyl-substituted derivatives of ailine andpyridine, such as 3-methyl-5-ethylaniline, 2,4,5-trimethylaniline,2,6-diethylaniline, 2-tert.-butylaniline, 3,4-diethylpyridine,2-ethyl5-propylpyridine, 2,4-diethy-l-3-methylpyridine,Z-butyl-S-methylpyridine, 2,6-dipropylpyridine and the like. Many ofthese compounds boil in a temperature range close to or overlapping thatof the desired product. As a result, the distillate recovered from sucha mixture by ordinary fractionation has often been found to consist ofno more than about 35 percent by weight of quinoline, an amount whichmay be considered insufiicient for the commercial production ofquinoline.

On the other hand, salts of many aromatic nitrogen bases, such as thephosphate or sulfate salts of alkylsubstituted derivatives of anilineand pyridine, evidence solubility characteristics in solvents such aswater and alcohols comparable to those possessed by like salts ofquinoline. Consequently, the separation of quinoline from an aromaticnitrogen base mixture by solvent ex traction techniques which aredependent upon the relative solubility of aromatic nitrogen base saltsin the solvents described is rendered less effective in terms of productyield and concentration as the initial concentration of these otheraromatic nitrogen bases in the mixture increases, and as theconcentration of quinoline therein decreases. k I

Advantageously, these difficulties can now be overcome through thepractice of the present invention, an object of which is to provide animproved process for the substantial recovery of quinoline from amixture with other aromatic nitrogen bases as a product of highconcentration. Another object of the invention is to provide an improvedprocess for recovering quinoline from aromatic nitrogen base mixtureswhich process is not closely dependent upon the initial concentration ofthe various components of the mixture. Still other objects andadvantages of the invention will become apparent in light of thefollowing description.

In its broadest aspect, the invention contemplates subjecting aquinoline-containing aromatic nitrogen base mixture to azeotropicdistillation in the presence of kerosene so as to obtain a distillatecomprised essentially of a minimum-boiling quinoline-kerosene azeotrope.The quinoline component can then be recovered from the azeotropicdistillate with facility in several different ways, as hereinafterdescribed, and subsequently purified if desired. In this manner, it ispossible to obtain a substantially pure product containing a quinolineconcentration of up toabout 99 percent or more by weight, andrepresenting a quinoline yield of up to about 93 percent or more byweight, even when the initial quinoline-containing mixture also containsappreciable quantities of closely related aromatic primary and tertiaryamines.

In the practice of the invention, it is preferred, although not criticalthereto, that the initial boiling point of the aromatic nitrogen basemixture subjected to azeotropic distillation be between about 230 C. andthe boiling point of quinoline, i.e., about 238 C., and more preferablybetween about 234 C. and about 238 C. Greater efliciency and economy ofoperation can thereby be realized for the reasons stated below.

The invention is based in important part upon the finding that kerosenewill azeotrope with quinoline, thus forming a mixture having a boilingpoint substantially below that of quinoline and many other aromaticnitrogen bases. In accordance with the invention, this azeotrope istaken advantage of to separate quinoline from the remaining componentsof the aromatic nitrogen base mixture.

In addition to quinoline, however, certain other compounds commonlypresent in aromatic nitrogen base mixtures have also been found to formminimum-boiling azeotropes with kerosene. Fortunately, the depression inboiling point as a result of kerosene azeotrope formation is generallynot as great with the other aromatic nitrogen bases as with quinoline,particularly at subatmospheric pressures. Hence, the low-boilingquinoline-keroseneazeotropes can be separated from many of thesecompounds during azeotropic distillation, preferably by carrying out thedistillation in a partial vacuum.

Nevertheless, the difiiculty and inconvenience encountered inengendering a substantially complete recovery of quinoline in highconcentration, due to the presence of other kerosene azeotropes, becomesincreasingly great as the initial boiling point of the aromatic nitrogenbases from which quinoline is to be recovered decreases below about 234C., and especially below about 230 C. Compounds boiling at such lowtemperatures, particularly low-boiling alkyl-substituted an-ilines, aremore likely to form azeotropes with kerosene which boil in approximatelythe same temperature range as the quinoline as contaminants in theazeotropic distillate. It is therefore expedient and preferable toeifect a preliminary separation or distillation of thequinoline-conta-ining aromatic nitrogen base mixture so that theazeotropic distillation can be directed specifically to a mixture havingan initial boiling point of at least about 230 C. and more preferably atleast about 234 C. In this manner, the need or desirability forsubsequent purification of the quinoline product diminishes as theinitial boiling point of the aromatic nitrogen base mixture isincreased. In addition, lesser quantities of kerosene are required forthe azeotropic distillation.

The preliminary separation or distillation of the ammatic nitrogen basemixture can be accomplished by any convenient means, either duringproduction of the mixture or subsequent thereto. In connection with theliquid-phase hydrogenation of coal, for example, thequinoline-containing mixture can be obtained as a fraction having thedesired initial boiling point by the exercise of control over theconventional distillation of the crude hydrogenation product.

In an embodiment of the invention, kerosene is suitably admixed with thequinoline-containing aromatic nitrogen base mixture and the resultingmixture introduced into a distillation zone. While quinoline has beenfound to azeotrope with a wide variety of hydrocarbons, particularlygood results can be obtained in the invention when the kerosene employedas azeotroping agent has an initial boiling point of at least about 190C., and preferably a boiling point range of between about 190 C. and theinitial boiling point of the aromatic nitrogen base mixture. Higher orlower boiling kerosene fractions can also be employed. However, as theboiling point of the kerosene fraction decreases, the proportion ofquinoline in the quinoline-kerosene azeotrope also decreases, often toan appreciable extent as the boiling point range of the kerosenefraction falls below 190 C. The yield of quinoline obtained uponsubsequent separation of the azeotropic distillate is therebydiminished, although the purity of the product, i.e., the concentrationof quinoline therein, remains unaffected. On the other hand, an increasein the boiling point of the kerosene fraction engenders an increase inthe boiling point of the quinoline-kerosene azeotrope thus renderingmore difficult the separation of the azeotrope from the remainingcomponents of the aromatic nitrogen base mixture.

The initial concentration of quinoline in the aromatic nitrogen basemixture together with other factors such as the boiling point range ofthe mixture, particularly the initial boiling point thereof, and theratio of quinoline to kerosene in the resulting azeotrope is generallydeterminative of the amount of kerosene required to permit thesubstantially complete recovery of quinoline. This amount can readily bedetermined by one skilled in the art. In this connection, a convenientexpression for the amount of kerosene to be employed, and one whichinherently takes into account any loss of kerosene, as for example, byazeotrope formation with other aromatic. nitrogen bases, is based uponthe total weight of the. mixture. Thus, high yields and concentration ofquinoline have been obtained when kerosene is admixed with analkyl-substituted anilines.

aromatic nitrogen base mixture produced by the liquidphase hydrogenationof coal in a proportion of from about 1 to about 2 parts by weight ofkerosene to each part by weights of the aromatic nitrogen base mixture.The amount of kerosene required is not narrowly critical, however, hencehigher and lower proportions of kerosene can be utilized in theinvention with satisfaction.

The azeotropic distillation can be carried out at any pressure up toabout 4 atmospheres, pressures above this level frequently engenderingthe breakdown of the azeotrope into its component parts. As mentionedabove, the azeot'ropic distillation is preferably conducted underreduced pressure in order to facilitate the separation of thequinoline-kerosene azeot-rope from other azeotrope-forming aromaticnitrogen bases, particularly Accordingly, reduced pressures of fromabout 10 to about 20 millimeters of mercury are most desirably employed.

The temperature at which the quinoline-kerosene azeotrope distills overis dependent in direct relationship to both the boiling range of thekerosene fraction and the pressure at which distillation is conducted,and can readily be determined by one skilled in the art. By way ofillustration, the quinoline-kerosene azeotrope boils at a temperature ofabout 110 C. when a kerosene fraction boiling in the temperature rangeof from about 225 C. to about 230 C., and a pressure of about 20millimeters of mercury are employed.

In a typical azeotropic distillation, heat is increasingly applied tothe mixture of kerosene and aromatic nitrogen bases in the distillationzone at the desired pressure until a temperature is reached at which thequinoline-kerosene azeotrope distills over. The distillation iscontinued at this temperature level until further quantities of thequinoline-kerosene azeotrope can no longer be recovered or until thetemperature of the reflux rises substantially above the boiling point ofthe azeotrope. The quinoline component can then be separated andrecovered from the azeotropic distillate in any suitable manner.

By way of illustration, a convenient and economical procedure involvescooling the azeotropic condensate to a temperature below about 20 C. andpreferably to a temperature between about 0 C. and 5 0, whereby a phaseseparation of the azeotrope is eifected. Thus, a quinoline-rich bottomlayer and a kerosene-rich upper layer are obtained and can be mutuallyseparated by decanation. The particular manner in which the separationof the azeotrope into its component parts is accomplished is not,however, critical to the invention.

For example, another suitable procedure lies in the extraction of thequinoline component by the addition of an aqueous mineral acid solutionsuch as an aqueous solution of hydrochloric acid to the az'eotropiccondensate. The quinoline-containing aqueous acidic layer thereby formedis readily separated from the kerosene component by decantation, andupon neutralization with caustic yields the desired product. In asimilar manner, the qu-inoline component can be separated and recoveredby extraction from the azeotropic condensate with water or an alcoholsuch as methanol.

If desired, the kerosene component of the azeotrope can be recycled tothe distillation zone where it is admixed with further quantities ofaromatic nitrogen base mixture. The recycling of kerosene in such amanner provides a continuous method for the recovery of quinoline from amixture with other aromatic nitrogen bases wherein a considerablesavings in the amount of azeotrope-forming agent is possible. However,the method of the invention can also be carried out efiiciently inbatchwise operation.

The quinoline product obtained by cooling or otherwise treating theazeotropic condensate as described above can thereafter be employed inprocedures involving the use of quinolines without further processing,or subjected to Conventional fractional distillation in order to providea quinoline product of higher concentration or purity. It is generallyfound desirable to upgrade the product in this manner when the initialboiling point of the aromatic nitrogen base mixture from which thecondensate was obtained was below about 234 C. and especially belowabout 230 C. Under these circumstances, varying amounts of otheraromatic nitrogen bases such as lowboiling alkyl-substituted anilinesmay also be distilled over as azeotropes with kerosene and appear ascontaminants in the quinoline product. However, their separation fromquinoline as forecuts during the fractional distillation of thequinoline product can readily be accomplished even at atmosphericpressure due to their significant difference in boiling points from thatof quinoline.

The improved process of the invention can also be illustrated bydescription in connection with the following specific examples of itspractice.

EXAMPLE 1 A crude product obtained by the conventional liquidphasehydrogenation of coal was distilled so as to obtain as a fractionalcondensate a mixture of aromatic nitrogen bases having a boiling pointrange of between about 235 C. and about 241 C. The condensate containedan initial quinoline concentration of about 27 percent by weight. Fivehundred grams of the aromatic nitrogen base mixture thus obtained wasthen introduced to a 2-liter still pot equipped with 2-foot packedcolumn, and 500 grams of a kerosene fraction having a boiling pointrange of between about 223 C. and 230 C. added thereto with stirring.Heat was applied to the still and the resulting mixture of aromaticnitrogen bases and kerosene subjected to azeotropic distillation under areduced pressure of about 20 millimeters of mercury. At a temperature ofabout 110 C. the formation of a distillate was observed. Heating wascontinued until the temperature of the reflux reached 115 C. Thedistillate was condensed and found by chemical analysis to be anazeotropic mix ture composed of about 32 percent by weight of aromaticnitrogen bases and about 68 percent by weight of kerosene. Theazeotropic condensate was then cooled to a temperature of about 5 C.Upon cooling, the azeotropic mixture separated into two layers, theupper layer of which was removed by decantation. Chemical andspectroscopic analysis indicated the presence of quinoline in the 132gram bottom layer in a concentration of about 91.0 percent by weightrepresenting a quinoline yield of about 97 percent, while the upperlayer was found to be composed essentially of kerosene. Thequinoline-rich bottom layer was then introduced to a small still andsubjected to fractional distillation at atmospheric pressure. At atemperature of about 237 C. a 117 gram fraction was recovered and foundby chemical and spectroscopic analysis to contain quinoline in aconcen-- tration of about 99.0 percent by weight, representing anoverall quinoline yield of about 86 percent.

The experiment was repeated employing a kerosene fraction having aboiling point range of between about 220 C. and 225 C. as theazeotroping agent. The azeotropic distillate was condensed and found bychemical analysis to be a mixture composed of about 26 percent by weightof aromatic nitrogen bases and about 74 percent by weight of kerosene.The ultimate yield and concentration of the quinoline product was thesame as that described above.

EXAMPLE 2 In a manner essentially the same as that described in Example1, 250 grams of an aromatic nitrogen base mixture obtained by theliquid-phase hydrogenation of coal, having a boiling point range ofbetween about 236 C. and about 238 C., and containing an initialquinoline concentration of about 88 percent by weight, was admixed with500 grams of a kerosene fraction having a boiling point range of betweenabout 225 C.

and about 230 C. and subjected to azeotropic distillation. -Theazeotropic mixture distilling over at a temperature of about 110 C.under a reduced pressure of EXAMPLE 3 In a manner similar to thatdescribed in Example 1, 350 grams of an aromatic nitrogen base mixtureobtained by the liquid-phase hydrogenation of coal, having a boilingpoint in the range of between about 235 C. and about 240 C. andcontaining an initial quinoline concentration of about 68 percent byweight, was admixed with 700 grams of a kerosene fraction having aboiling point range of between about 223 C. and 228 C., and subjected toazeotropic distillation. During distillation at a temperature of about110 C. and under a reduced pressure of about 20 millimeters of mercury,several azeotropic fractions were taken and condensed. Each fraction wasthen treated with from about to 200 grams of a 6 normalaqueoushydrochloric acid solution, whereupon an aqueous acidic bottomlayer and. a kerosene upper layer were formed. The kerosene layer wasremoved by decantation and the bottom layer neutralized by the additionof from about 100 to 200 grams of a 6 normal aqueous sodium hydroxidesolution. Upon neutralization, an aromatic nitrogen base layer wasseparated and recovered by decantation. The aromatic nitrogen baseproduct obtained from each fraction was then analyzed for the presenceof aromatic primary, secondary and tertiary amines by selectivetitration, and specifically for the presence of quinoline by infra-redanalysis. The results obtained are set forth below in Table A. In thetable, the percent by weight of the aromatic nitrogen base mixture whichhad been distilled over as an azeotrope with kerosene upon the taking ofeach fraction is indicated in the column headed Amount Distilled; theconcentration of aromatic amines in the product is indicated as moles ofamine per 100 grams of product; the concentration of quinoline in theproduct is indicated as percent by weight of the product.

Table A Concentration of Aromatic Amines Concen- Fraction No. Amounttration Distilled of Quinc- Primary Secon- Tertiary line dary From theabove table it can be seen that in accordance with the process of theinvention, quinoline can be recovered from a mixture with other aromaticnitrogen.

prised essentially of a quinoline-kerosene azeotrope and separating thequinoline component from said distillate. 2. A process for the recoveryof quinolinefrom a mixture with other aromatic nitrogen bases, saidmixture having an initial boiling point of between about 230 C. andabout 238 C., which comprises subjecting said mixture to azeotropicdistillation in the presence of a kerosene fraction having an initialboiling point of at least about 190 C. so as to obtain a distillatecomprised essentially of a quinoline-kerosene azeotrope, condensing thedistillate and separating the quinoline component from the condensate.

3. A process for the recovery of quinoline from a mixture with otheraromatic nitrogen bases, said mixture having an initial boiling point ofbetween about 230 C. and about 238 C. which comprises subjecting saidmixture to azeotropic distillation under reduced pressure in thepresence of a kerosene fraction having a boiling point range of betweenabout 190 C. and the initial boiling point of the aromatic nitrogen basemixture so as to obtain a distillate comprised essentially of aquinoline-kerosene azeotrope, condensing the distillate, cooling thecondensate to a temperature below about 20 C., thereby efiecting a phaseseparation of the condensate into a quinolinerich layer and akerosene-rich layer and separating the quinoline-rich layer from thecondensate and subjecting the quinoline-rich layer to furtherdistillation so as to obtain a distillate consisting of substantiallypure quinoline.

4. A process for the recovery of quinoline from a mixture with otheraromatic nitrogen bases, said mixture having an initial boiling point ofbetween about 230 C. and about 238 C. which comprises subjecting saidmixture to azeotropic distillation under reduced pressure in thepresence of a kerosene fraction having a boiling point range of betweenabout 190 C. and the initial boiling point of the aromatic nitrogen basemixture so as to obtain a distillate comprised essentially of aquinoline-kerosene azeotrope, condensing the distillate, cooling thecondensate to a temperature below about 20 C., thereby effecting a phaseseparation of the condensate into a quinolinerich layer and akerosene-rich layer separating the quinoline-rich layer from thecondensate.

5. A process for the recovery of quinoline from a mixture with otheraromatic nitrogen bases, said mixture having an initial boiling point ofbetween about 230 C. and about 238 C., which comprises subjecting saidmixture to azeotropic distillation under reduced pressure in thepresence of a kerosene fraction having a boiling point range of betweenabout 190 C. and the initial boiling point of the aromatic nitrogen basemixture so as to obtain a distillate comprised essentially of aquinoline-kerosene azeotrope, condensing the distillate, cooling thecondensate to a temperature of between about C. and about C., therebyeffecting a phase separation of the condensate into a quinoline-richlayer and a kerosene-rich layer, separating the quinoline-rich layerfrom the condensate, recycling the kerosene-rich layer to the azeotropicdistillation and subjecting the quinoline-rich layer to furtherdistillation so as to obtain a distillate consisting of substantiallypure quinoline.

6. A process for the recovery of quinoline from a mixture with otheraromatic nitrogen base compounds, said mixture having an initial boilingpoint of between about 234 C., and about 238 C. which comprisessubjecting said mixture to azeotropic distillation in the presence of akerosene fraction having an initial boiling point of at least about 190C. so as to obtain a distillate comprised essentially of aquinoline-kcrosene azeo'trope, condensing the distillate and separatingthe quinoline component from the condensate.

7. A process for the recovery of qu'inoline from a mixture with otheraromatic nitrogen base compounds, said mixture having an initial boilingpoint of between about 234 C., and about 238 C. which comprisessubjecting said mixture to azeotropic distillation under reducedpressure in the presence of a kerosene fraction having a boiling pointrange of between about 190 C. and the initial boiling point of thearomatic nitrogen base 8 mixture so as to obtain a distillate comprisedessentially of a quinoline-kerosene azeotrope, condensing thedistillate, cooling the condensate to a temperature below about 20 C.,thereby eifecting a phase separation ofthe condensate into aquinolinerich layer and a kerosene-rich layer and separating thequinoline-rich layer from the condensate and subjecting thequinolinerrich layer to fur: ther distillation so as to obtain adistillate consisting of substantially pure quinoline.

8. A process for the recovery of quinoline from a mixture with otheraromatic nitrogen base compounds, said mixture having an initial boilingpoint of between about 234 C., and about 238 C. which comprisessubjecting said mixture to azeotropic, distillation under reducedpressure in the presence of a kerosene fraction having a boiling pointrange of between about C. and the initial boiling point of the aromaticnitrogen base mixture so as to obtain a distillate comprised essentialiyof a quinoline-kerosene azeotrope, condensing the distillate, coolingthe condensate to a temperature below about 20 C., thereby effecting aphase separation of the condensate into a quinoline-rich layer and akerosene- :rich layer separating the quinoline-rich layer from thecondensate.

9. A process for the recovery of quinoline from a mixture with otheraromatic nitrogen base compounds, said mixture having an initial boilingpoint of between about 234 C., and about 238 C. which comprisessubjecting said mixture to azeotropic distillation under re ducedpressure in the presence of a kerosene fraction having a boiling pointrange of between about 190 C. and the initial boiling point of thearomatic nitrogen base mixture so as to obtain a distillate comprisedessentially of a quinolinekerosene azeotrope, condensing the distillate,cooling the condensate to a temperature of between about 0 C. and about5 C., thereby effecting a phase separation of the condensate into aquinoline-rich layer and a kerosene-rich layer, separating thequinoline-rich layer from the condensate, recycling the kerosene-richlayer to the azeotropic distillation and subjecting the quinoline-richlayer to further distillation so as to obtain a distillate consisting ofsubstantially pure quinoline.

10. In a process for the production of quinoline by the liquid-phasehydrogenation of coal wherein an aromatic nitrogen base-containing crudehydrogenation product is obtained, from which quinoline is subsequentlyrecovered, that improvement which comprises subjecting the aromaticnitrogen base fraction of the crude hydrogenation product to azeotropicdistillation in the presence of kerosene so as to obtain a distillatecomprised essentially of a quinoline-kerosene azeotrope and separatingthe quinoline component from said distillate.

11. In a process for the production of quinoline by the liquid-phasehydrogenation of coal wherein an aromatic nitrogen base-containing crudehydrogenation product is obtained, from which quinoline is subsequentlyrecovered, that improvement which comprises subjecting the aromaticnitrogen base fraction of the crude hydrogenation product having aninitial boiling point of between about 230 C. and about 238 C., toazeotropic distillation in the presence of from about 1 to about 2 partsby weight of the aromatic nitrogen base fraction of a kerosene fractionhaving an initial boiling point of at least about 190 C. so as to obtaina distillate comprised essentially of a quinoline-kerosene azeotrope,condensing the distillate and separating the quinoline component fromthe con densate.

12. In a process for the production of quinoline by the liquid-phasehydrogenation of coal wherein an aromatic nitrogen base-containing crudehydrogenation product is obtained, from which quinoline is subsequentlyrecovered, that improvement which comprises subjecting the nitrogen basefraction of the crude hydrogenation prodnot having an initial boilingpoint of between about 230 C. and about 238 C. to azeotropicdistillation in the presence of from about 1 to about 2 parts by weightof the aromatic nitrogen base fraction of a kerosene fraction having aboiling point range of between about 190 C. and the initial boilingpoint of the aromatic nitrogen base mixture so as to obtain a distillatecomprised essentially of quinoline-kerosene azeotrope, condensing thedistillate, cooling the condensate to a temperature below about 20 C.,thereby effecting a phase separation of the condensate into aquinoline-rich layer and a kerosenerich layer and separating thequinoline-rich layer from the condensate and subjecting thequinoline-rich layer to further distillation so as to obtain adistillate consisting of substantially pure quinoline.

13. In a process for the production of quinoline by the liquid-phasehydrogenation of coal wherein an arcmatic nitrogen base-containing crudehydrogenation prod not is obtained, from which quinoline is subsequentlyrecovered, that improvement which comprises subjecting the aromaticnitrogen base fraction of the crude hydrogenation product having aninitial boiling point of between about 230 C. and about 238 C. toazeotropic distillation in the presence of from about 1 to about 2 partsby weight of the aromatic nitrogen base fraction of a kerosene fractionhaving a boiling point range of between about 190 C. and the initialboiling point of the aromatic nitrogen base mixture so as to obtain adistillate comprised essentially of a quinoline-kerosene azeotrope,condensing the distillate, cooling the condensate to a temperature belowabout 20 0., thereby effecting a phase separation of the condensate intoa quinoline-rich layer and a kerosene-rich layer separating thequinoline-rich layer from the condensate.

14. In a process for the production of quinoline by the liquid-phasehydrogenation of coal wherein an arcmatic nitrogen base-containing crudehydrogenation product is obtained, from which quinoline is subsequentlyrecovered, that improvement which comprises subjecting the aromaticnitrogen base fraction of the crude hydrogenation product having aninitial boiling point of between about 230 C. and about 238 C. toazeotropic distillation in the presence of from about 1 to about 2 partsby weight of the aromatic nitrogen base fraction of a kerosene fractionhaving a boiling point range of be tween about 190 C. and the initialboiling point of the aromatic nitrogen base mixture so as to obtain adistillate comprised essentially of a quinoline-kerosene azeotrope,condensing the distillate, cooling the condensate to a temperature ofbetween about C. and about 5 C., thereby efiecting a phase separation ofthe condensate into a quinoline-rich layer and a kerosene-rich layer,separating the quinoline-rich layer from the condensate, recycling thekerosene-rich layer to the azeotropic distillation and subjecting thequinoline-rich layer to further distillation so as to obtain adistillate consisting of substantially pure quinoline.

15. In a process for the production of quinoline by the liquid-phasehydrogenation of coal wherein an aromatic nitrogen base-containing crudehydrogenation product is obtained, from which quinoline is subsequentlyrecovered, that improvement which comprises subjecting the aromaticnitrogen base fraction of the crude hydrogenation product having aninitial boiling point of between about 234 C. and about 238 C. toazeotropic distillation in the presence of from about 1 to about 2 partsby weight of the aromatic nitrogen base fraction of a kerosene fi'actionhaving an initial boiling point of at least about 190 C. so as to obtaina distillate comprised essentially of a quinoline-kerosene azeotrope,condensing the distillate and separating the quinoline component fromthe condensate.

16. In a process for the production of quinoline by the liquid-phasehydrogenation of coal wherein an aromatic nitrogen base-containing crudehydrogenation prodnot is obtained, from which quinoline is subsequentlyrccovered, that improvement which comprises subjecting the aromaticnitrogen base fraction of the crude hydrogenation product having aninitial boiling point of between about 234 C. and about 238 C. toazeotropic distillation in the presence of from about 1 to about 2 partsby weight of the aromatic nitrogen base fraction of a kerosene fractionhaving a boiling point range of between about C. and the initial boilingpoint of the aromatic nitrogen base mixture so as to obtain a distillatecomprised essentially of a quinoline-kerosene azeotrope, condensing thedistillate, cooling the condensate to a temperature below about 20 C.,thereby effecting a phase separation of the condensate into aquinoline-rich layer and a kerosene-rich layer and separating thequinoline-rich layer from the condensate and subjecting thequinoline-rich layer to further distillation so as to obtain adistillate consisting of substantially pure quinoline.

17. In a process for the production of quinoline by the liquid-phasehydrogenation of coal wherein an aromatic nitrogen base-containing crudehydrogenation product is obtained, from which quinoline is subsequentlyrecovered, that improvement which comprises subjecting the aromaticnitrogen base fraction of the crude hydrogenation product having aninitial boiling point of between about 234 C. and about 238 C. toazeotropic distillation in the presence of from about 1 to about 2 partsby weight of the aromatic nitrogen base fraction of a kerosene fractionhaving a boiling point range of between about 190 C. and the initialboiling point of the aromatic nitrogen base mixture so as to obtain adistillate comprised essentially of a quinoline-kerosene azeotrope,condensing the distillate, cooling the condensate to a temperature belowabout 20 0., thereby efiiecting a phase separation of the condensateinto a quinoline-rich layer and a kerosene-rich layer separating thequinoline-rich layer from the condensate.

18. In a process for the production of quinoline by the liquid-phasehydrogenation of coal wherein an aromatic nitrogen base-containing crudehydrogenation prodnot is obtained, from which quinoline is subsequentlyrecovered, that improvement which comprises subjecting the aromaticnitrogen base fraction of the crude hydrogenation product having aninitial boiling point of between about 234 C. and about 238 C. toazeotropic distillation in the presence of from about 1 to about 2 partsby weight of the aromatic nitrogen base fraction of a kerosene fractionhaving a boiling point range of between about 190 C. and the initialboiling point of the aromatic nitrogen base mixture so as to obtain adistillate comprised essentially of a quinoline-kerosene azeotrope,condensing the distillate, cooling the condensate to a temperature ofbetween about 0 C. and about 5 C., thereby effecting a phase separationof the condensate into a quinoline-rich layer and a kerosene-rich layer,separating the quinoline-rich layer from the condensate, recycling thekerosene-rich layer to the azeotropic distillation and subjecting thequinoline-rich layer to further distillation so as to obtain adistillate consisting of substantially pure quinoline.

References Cited in the file of this patent UNITED STATES PATENTS2,035,583 Bailey Mar. 31, 1936 2,085,287 Bailey June 29, 1937 2,231,241Bailey Feb. 11, 1941 2,237,542 Bailey Apr. 8, 1941 2,363,159 Engel Nov.21, 1944 OTHER REFERENCES Distillation (Weissberger), published byInterscience Publishers Inc. (N.Y.), 1951, pages 356-368 relied upon.

1. A PROCESS FOR THE RECOVERY OF QUINOLINE FROM A MIXTURE WITH OTHERAROMATIC NITROGEN BASES WHICH COMPRISES SUBJECTING SAID MIXTURE TOAZEOTROPIC IN THE PRESENCE OF KEROSENE SO AS TO OBTAIN A DISTILLATECOMPRISED ESSENTIALLY OF A QUINOLINE-KEROSENE AZEOTROPE AND SEPARTINGTHE QUINOLINE COMPONENT FROM SAID DISTILLATE.